Hepatitis C virus (HCV) infection is the most common chronic blood-borne infection in the United States. The Center for Disease Control (CDC) estimates that during the 1980's, an average of 230,000 new infections occurred each year. The CDC also estimates that the prevalence of HCV in the U.S. will triple between now and the year 2010.
HCV is one of the most important causes of chronic liver disease in the United States. It accounts for about 20 percent of acute viral hepatitis, 60 to 70 percent of chronic hepatitis, and 30 percent of cirrhosis, end-stage liver disease, and liver cancer. Almost 4 million Americans, or 1.8 percent of the U.S. population, have antibody to HCV (anti-HCV), indicating ongoing or previous infection with the virus. Hepatitis C causes an estimated 8,000 to 10,000 deaths annually in the United States.
Chronic hepatitis C can cause cirrhosis, liver failure, and liver cancer. About 20 percent of patients develop cirrhosis within 10 to 20 years of the onset of infection. Liver failure from chronic hepatitis C is one of the most common reasons for liver transplants in the United States. Hepatitis C might be the most common cause of primary liver cancer in the developed world. In Italy, Spain, and Japan, at least half of liver cancers could be related to HCV. Males, alcoholics, patients with cirrhosis, people over age 40, and those infected for 20 to 40 years are more likely to develop HCV-related liver cancer.
Chronic hepatitis C varies greatly in its course and outcome. At one end of the spectrum are patients who have no signs or symptoms of liver disease and completely normal levels of serum liver enzymes. Liver biopsy usually shows some degree of chronic hepatitis, but the degree of injury is usually mild, and the overall prognosis may be good. At the other end of the spectrum are patients with severe hepatitis C who have symptoms, HCV RNA in serum, and elevated serum liver enzymes, and who ultimately develop cirrhosis and end-stage liver disease. In the middle of the spectrum are many patients who have few or no symptoms, mild to moderate elevations in liver enzymes, and an uncertain prognosis.
Currently in the United States, two different regimens have been approved as therapy for hepatitis C: Monotherapy with alpha interferon and combination therapy with alpha interferon and ribavirin. Combination therapy consistently yields higher rates of sustained response than does monotherapy. Both methods of treatment have multiple side effects. Additionally, few options exist for patients who either do not respond to therapy or who respond and later relapse. Combination treatment is more expensive and is associated with more side effects than monotherapy, but, in most situations, it is preferable. Even for patients that do respond, the side effects may be intolerable.
As is evident from the foregoing, new medications and approaches to the treatment of HCV are needed.